Not applicable.
Not applicable.
1. Field of the Invention
The present invention relates generally to logging tool conveyance methods for highly deviated or horizontal wells. More specifically, the invention relates to downhole tractor tools that may be used to convey other logging tools in a well.
2. Background Art
The invention is a device that selectively grips or releases the well wall. It can also position the tractor tool at the center of the well bore.
Once a well is drilled, it is common to log certain sections of it with electrical instruments. These instruments are sometimes referred to as xe2x80x9cwirelinexe2x80x9d instruments, as they communicate with the logging unit at the surface of the well through an electrical wire or cable with which they are deployed. In vertical wells, often the instruments are simply lowered down the well on the logging cable. In horizontal or highly deviated wells, however, gravity is frequently insufficient to move the instruments to the depths to be logged. In these situations, it is necessary to use alternative conveyance methods. One such method is based on the use of downhole tractor tools that run on power supplied through the logging cable and pull or push other logging tools along the well.
Downhole tractors use various means to generate the traction necessary to convey logging tools. Some designs employ powered wheels that are forced against the well wall by hydraulic or mechanical actuators. Others use hydraulically actuated linkages to anchor part of the tool against the well wall and then use linear actuators to move the rest of the tool with respect to the anchored part. A common feature of all the above systems is that they use xe2x80x9cactivexe2x80x9d grips to generate the radial forces that push the wheels or linkages against the well wall. The term xe2x80x9cactivexe2x80x9d means that the devices that generate the radial forces use power for their operation. The availability of power downhole is limited by the necessity to communicate through a long logging cable. Since part of the power is used for actuating the grip, tractors employing active grips tend to have less power available for moving the tool string along the well. Thus, an active grip is likely to decrease the overall efficiency of the tractor tool. Active grips have another disadvantage. This is the relative complexity of the device and, hence, it""s lower reliability. A more efficient and reliable gripping device can be constructed by using a passive grip that does not require power for the generation of high radial forces. In one such design, the gripping action is achieved through sets of arcuate-shaped cams that pivot on a common axis located at the center of the tool. This gripping system allows the tractor tool to achieve superior efficiency. However, by virtue of the physics of their operation, the cams allow tractoring in only one (downhole) direction. Another limitation of this system is the relatively narrow range of well bore sizes in which these cams can operate. In addition, the cams cannot centralize the tool by themselves. This requires the usage of dedicated centralizers, which increase the tractor tool length.
Downhole tractor tools that use various methods of operation to convey logging tools along a well have been previously disclosed and are commercially available.
U.S. Pat. No. 6,179,055 discloses a conveyance apparatus for conveying at least one logging tool through an earth formation traversed by a horizontal or highly deviated borehole. The conveyance apparatus comprises a pair of arcuate-shaped cams pivotally mounted to a support member, a spring member for biasing the arcuate surface of each cam into contact with the borehole wall, and actuators operatively connected to each cam. A logging tool is attached to the conveyance apparatus. When either actuator is activated in a first direction, the cam connected to the activated actuator is linearly displaced forward and the arcuate surface of the cam slides along the borehole wall. When either actuator is activated in a second direction, the activated actuator pulls the connected cam backwards and the spring member thereby urges the arcuate surface of the cam to lock against the borehole wall. Once the cam is locked, further movement of the actuator propels both the conveyance apparatus and the logging tool forward along the highly deviated or horizontal borehole.
U.S. Pat. No. 6,089,323 discloses a tractor system which, in certain embodiments, includes a body connected to an item, first setting means on the body for selectively and releasably anchoring the system in a bore, first movement means having a top and a bottom, the first movement means on the body for moving the body and the item, the first movement means having a first power stroke, and the tractor system for moving the item through the bore at a speed of at least 10 feet per minute.
U.S. Pat. No. 6,082,461 discloses a tractor system for moving an item through a wellbore with a central mandrel interconnected with the item, first setting means about the central mandrel for selectively and releasably anchoring the system in a wellbore, the central mandrel having a top, and a bottom, and a first power thread therein, the first setting means having a first follower pin for engaging the first power thread to power the first setting means to set the first setting means against an inner wall of the bore. In one aspect, the tractor system is for moving the item through the bore at a speed of at least 10 feet per minute. In one aspect, the tractor system has second setting means on the central mandrel for selectively and releasably anchoring the system in the bore, the second setting means spaced apart from the first setting means, and the central mandrel having a second power thread therein and a second retract thread therein, the second retract thread in communication with the second power thread, and the second setting means having a second follower pin for engaging the second power thread to power the second setting means to set the second setting means against the inner wall of the bore.
U.S. Pat. No. 5,954,131 discloses a conveyance apparatus for conveying at least one logging tool through an earth formation traversed by a horizontal or highly deviated borehole. The conveyance apparatus comprises a pair of arcuate-shaped cams pivotally mounted to a support member, means for biasing the arcuate surface of each cam into contact with the borehole wall, and actuators operatively connected to each cam. A logging tool is attached to the conveyance apparatus. When either actuator is activated in a first direction, the cam connected to the activated actuator is linearly displaced forward and the arcuate surface of the cam slides along the borehole wall. When either actuator is activated in a second direction, the activated actuator pulls the connected cam backwards and the biasing means thereby urges the arcuate surface of the cam to lock against the borehole wall. Once the cam is locked, further movement of the actuator propels both the conveyance apparatus and the logging tool forward along the highly deviated or horizontal borehole.
U.S. Pat. No. 5,184,676 discloses a self-propelled powered apparatus for traveling along a tubular member that includes power driven wheels for propelling the apparatus, a biasing means for biasing the driven wheels into contact with the inner surface of the tubular member, and a retracting means for retracting the driven wheels from the driving position so that the apparatus can be withdrawn from the tubular member. The retracting means also include means to automatically retract the driven wheels from the driving position when the power to the apparatus is cut-off.
One embodiment of the invention comprises a linkage apparatus for selectively gripping and releasing the inside walls of a conduit, the apparatus comprising: a first arm; a bi-directional gripping cam rotatably attached to the arm; and an extension and locking device adapted to selectively radially extend the arm from a tool housing to an inside wall of a conduit and adapted to selectively lock the arm in an extended position.
Another embodiment of the invention comprises an apparatus for selectively gripping and releasing the inside wall of a conduit, the apparatus comprising: a plurality of linkages, each linkage comprising a first arm having a first end and a second end; a second arm having a first end and a second end, the second end of the first arm pivotably attached to the second end of the second arm, and a bi-directional gripping cam rotatably attached to at least one of the second end of the first arm and the second end of the second arm; a grip body, the first end of the first arm pivotably attached to the grip body; a hub, adapted to slide relative to the grip body, the first end of the second arm pivotably attached to the hub; and an extension and locking device adapted to selectively radially extend the linkages from the grip body and adapted to selectively lock the linkages in an extended position.
Another embodiment of the invention comprises a method for conveying a tool body through a conduit, comprising: moving a bi-directional gripping cam into contact with an inner wall of a conduit; laterally locking a position of the cam; and moving the tool body axially with respect to the cam in a first direction.
Advantages of the invention include one or more of the following:
A device that acts as a tool centralizer;
A device that selectively grips or releases the inside walls of a circular conduit such as a well or a pipe;
A device with an extended operational range of well bore sizes;
A device having double-sided cams that can grip in both the downhole and uphole directions;
A device that provides superior efficiency and reliability; and
A device having a passive grip system;
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.